Induction of pulsatile LH release, FSH release and ovulation in post-partum acyclic beef cows by repeated small doses of Gn-RH.
Five acyclic spring-calving beef cows (20-40 days post partum) were bled every 15 min for 60 h and thereafter every 6 h for 5 days. Gn-RH (5 micrograms) was injected every 2 h for 48 h, starting 12 h after sampling began. Pulsatile patterns of LH release occurred synchronously in response to injection and 4 of the 5 treated animals subsequently ovulated and completed at least one full ovarian cycle. Four of 6 similar control cows were bled every 10 min for 8-h periods at equivalent times post partum. Pulses of LH were seen after approximately Day 25 post partum with a mean pulse frequency of 0.5 per h. There was little evidence of a discrete pulsatile mode of FSH release in any of the treated or control cows. The time to the first significant progesterone rise in the 4 treated and ovulating cows (34.5 +/- 5.6 days post partum) was significantly shorter (P less than 0.05) than in the 6 control animals (66.3 +/- 11.4 days).
D000818:Animals; D002417:Cattle / Q000502:physiology*; D005260:Female; D005640:Follicle Stimulating Hormone / Q000378:metabolism*; D007986:Luteinizing Hormone / Q000378:metabolism*; D008892:Milk / Q000032:analysis; D010062:Ovulation Induction / Q000662:veterinary*; D010906:Pituitary Hormone-Releasing Hormones / Q000494:pharmacology*; D049590:Postpartum Period; D011247:Pregnancy; D011374:Progesterone / Q000032:analysis; D011863:Radioimmunoassay; D012636:Secretory Rate
D010906:Pituitary Hormone-Releasing Hormones; D011374:Progesterone; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone